致命错误函数必须是一个字符串

<?php
    if(isset($_POST['submit'])){


        mysql_connect('localhost','root','');
        $con_db=mysql_select_db('test');

        if(!$con_db)echo"Error Connecting";

        $imageName = mysql_real_escape_string($_FILES['image']['name']);
        $imageData = mysql_real_escape_string(file_get_contents($_FILES['image']['tmp_name']));
        $imageType = mysql_real_escape_string($_FILES['image']['type']);

        echo $imageName;


        if(substr($imageType,0,5)=="image"){
            mysql_query('insert into image values("","$imageData","imageName")');
        }
        else echo "Select Image to Post";
    }
?>
<body>
    <form action="" method="post" enctype="multipart/form-data">
        <table>
            <td><tr>Upload image</tr><td><input type="file" name="image"></td>
            <td><tr></tr><tr><input type="submit" name="submit"></tr></td>

        </table>

I here have created a form and tried to upload the pic it got uploaded when i try to show the uploaded image its showing that there is a fatal error function must be a string

<?php
        $my_con=mysql_connect('localhost','root','');
        mysql_select_db('test');

        $getid = $_GET('id');

        if(isset($getid)){
            $id = $getid;
            $db_query = mysql_query("select * from 'image' where id='$id'");
            while($row = mysql_fetch_row($db_query)){
                $imageData = $row['image'];
            }
            header("content-type: image");
        }
        else{
            echo "Error!";  
        }
    ?>

This is another php file to display the image